The present invention relates to an apparatus which applies interlocking profile strips or xe2x80x9czippersxe2x80x9d to a web. Particularly, the invention relates to an apparatus which applies plastic extruded interlocking profile zippers bonded transversely at regular intervals to a length of plastic film.
U.S. Pat. No. 4,655,862 describes a method of making reclosable bags and material for making bags, including an apparatus wherein extruded fastener strips for reclosable bags are located across the longitudinal formation axis of the bag wall web material.
FIG. 13 of this reference illustrates a fastener strip applicator which uses a rotary drum adapted to be rotatably driven in step-by-step coordination with a form, fill, and seal apparatus. For preforming a large endless sheet quantity of the bag making web including fastener strip sections attached for future use, the applicator drum is rotated continuously for applying the strip sections to the continuously traveling web at bag length intervals. The drum is provided with axially extending pockets for receiving fasteners. A loader loads the proper length fastener strip section into one of the pockets, with the profiles extending inwardly toward the root of the channel-like pocket. A vacuum source may be applied to the pocket being loaded to hold the fastener therein. The loaded pocket then moves with rotation of the drum to a heating station where a heating roll heats the exposed base of the fastener strip. From the heating station, the strip is moved by rotation of the drum for application to the web. A heated rotatably driven roll may be provided to underlie the web across from the drum. The preheated fastener strip is brought into position for bonding to the web. At this point in the process, a positive pneumatic pressure is applied to the strip carrying pocket to apply a bonding pressure to the strip backed up by the roll. The bonded fastener then exits the pocket. The pocket advances toward the loading station to be reloaded with another fastener.
It would be desirable to provide a continuous, automated apparatus for preparing zippers, loading zippers onto a applying device for placing zippers onto a film, and successively attaching the zippers onto the film in precise spaced apart locations.
The present invention provides a continuous assembly apparatus for bonding extruded plastic strip fasteners or xe2x80x9czippersxe2x80x9d transversely at regular intervals to a printed or unprinted web.
The invention contemplates an apparatus for applying zippers to a web such as a plastic film, including: at least one draw roll for pulling a length of film past a zipper applying station; a turret located at said zipper applying station and arranged adjacent a length of film, the turret having spaced apart grooves therein around an outer surface thereof, each groove for holding a zipper therein, the turret driven in rotation to position successive grooves across a surface of the film; a zipper placing mechanism for placing successive zippers into successive grooves of the rotating turret; and a zipper feed mechanism for indexing a length of zipper material from an elongate supply of zipper material into the zipper placing mechanism, and for cutting off the length from the elongate supply of zipper material, the length corresponding to one zipper.
The preferred embodiment apparatus performs: a continuous unwind of film, an indexed progression of a length of the film, a continuous progression of zipper material laterally toward the length of film, an indexed progression of the zipper material, a fusing of male and female interlocking portions of the zipper material, a cutting of zipper material into individual zippers, a placing of individual zippers to a surface of the film, an attachment of the individual zippers to the film, and a continuous rewind of the zippered film into a roll of bag mating film stock.
At an upstream end in a processing direction of the film through the apparatus, an unwind stand includes a supply of film wound on a supply roll. The film is unwound by turning the supply roll, and is threaded through a dancer roll station for adjusting tension of the film and the speed of the supply roll.
The film is delivered to an infeed station. The infeed station provides for a continuous-to-intermittent motion of the film through use of an infeed dancer roll station. The dancer roll station creates a repeating accumulation of film which acts as a buffer during apparatus operation.
At a zipper applying station downstream of the infeed station the film is processed in an intermittent fashion: draw film, apply zipper, draw film, etc. During operation, the film is indexed in precise increments, e.g., one package length, into the body of the zipper applying station. This indexing can be done xe2x80x9cin registerxe2x80x9d if the film is printed.
An outfeed station located downstream of the zipper applying station includes a downstream set of draw rolls which feeds film out to a single, or multiple roll outfeed dancer roll station. This outfeed dancer roll station accumulates each indexed draw of film. The accumulation is fed out of the outfeed dancer roll station by a downstream set of nip rolls that are driven at the same speed as the infeed and speed trimmed by the outfeed dancer. Thus the film is fed out of the outfeed station at the same average speed as it is fed into the infeed station.
At a mid span of the apparatus is located the zipper applying station. Here, a prepared zipper is placed on a turret, the turret is rotated into position with the zipper underlying the film, and the zipper is sealed onto the film with a heat sealer.
The turret includes sealing platens providing grooves which receive individual zippers successively. The turret is mounted so that the sealing platens are elongated perpendicular to the direction in which the film flows. The sealing platens are spaced apart around the perimeter of the turret, rotatable to positions corresponding to turret stations. The turret stations on the turret rotate about an axis perpendicular to the direction of film flow.
The turret has a plurality of turret stations. In a presently preferred embodiment four turret stations are used but more or less than four is contemplated by the invention. In operation, a bottom station receives a new zipper, while the next station is preheated and or inspected by a sensor for the presence of a zipper and/or a peel seal is produced. A station on top of the turret is applying a zipper to the film. The fourth station, one position clockwise from the top, is idle.
Each rotational quarter cycle simultaneously applies a zipper, loads a new zipper, preheats a loaded zipper, and checks to see that there is a zipper in the station that is next set for application.
Zipper material in the form of interlocked profile strips, typically includes first and second interlocked bodies and film body flange portions connected to the bodies. The interlocked bodies typically have an engagable rib and groove interface which can be repeatedly opened and closed. Such zipper material is described for example in U.S. Pat. No. 5,461,845.
Zipper material composed of two elongate interlocked profile strips, is pulled from a zipper unwind stand by a set of servo-driven nip rolls. The zipper material is pulled in a direction perpendicular to the film flow direction in the zipper applying station. A zipper material dancer roll station allows for an indexed feed of zipper lengths from a continuous feed from a zipper material supply roll located on the zipper unwind stand.
The zipper material from the zipper unwind stand is conditioned by a zipper preparation device. The zipper preparation devices intermittently xe2x80x9ccrushesxe2x80x9d the continuous zipper material synchronized with each time the zipper material stops to be cut off into an individual zipper. This xe2x80x9ccrushxe2x80x9d is done by a device which welds the interlocking bodies of the zipper material together and flattens them. At a middle portion of this flattened spot, the zipper will be cut at a cutting station further downstream in the direction of zipper material flow. Thus, each individual zipper is separated from the zipper material with one-half of a crushed spot on each end.
Crushing serves two purposes, mechanically bonding of the two mating zipper parts and also making a barrier seal possible. The crush is not limited to the spine of the zipper but may include the flange portion or some part of the flange portion.
The zipper material is fed to length into a tray of a zipper receiving station and held there by a subsequent clamping action. Through an upward thrust of the tray, the zipper material is placed on the turret, clamped and cut simultaneously. The zipper material is clamped on both sides of a knife at the cutting station as the knife completes its cutting stroke.
The uppermost turret position is the sealing station where the zipper body flange portions are sealed to the film. A zipper that was earlier put onto the bottom station of the turret and held by vacuum, rests freely, or under reduced vacuum, at the sealing station on top of the turret.
A heated seal bar is pressed down onto the film and presses the film against the zipper, and both against the sealing platen. Heat is transferred through the film to the zipper body flange portion and the zipper is thus fastened to the film.
As additional features of the invention, a provision for sensing the absence of a zipper or a mis-applied zipper misaligned in the turret, during processing is contemplated. Initially, a zipper is sensed on the turret at a position between the loading station and the sealing station. Absence of a zipper, and/or a misapplied zipper here will cause a warning flag to be attached downstream in the film direction. Absence of and/or misapplication of two successive zippers will stop machine. Other control schemes are possible.
A rewind stand receives the film from the outfeed station. The rewind stand includes a tension dancer roll system for insuring proper tension during rolling up of the zippered film. A rewind roll winds up the zippered film at a substantially continuous rotation.
Thus, the invention provides a continuous manufacturing apparatus which effectively and efficiently applies zippers transversely to a moving film supplied from a continuously rotating supply roll, and rewinds the zippered film onto a continuously rotating rewind roll.
Other features and advantages of the present invention will become readily apparent from the following detailed description of the accompanying drawings, and the appended claims.